From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | lockhart(at)alumni(dot)caltech(dot)edu (Thomas G(dot) Lockhart) |
Cc: | daveh(at)insightdist(dot)com, hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] OR clause status |
Date: | 1998-08-06 15:37:25 |
Message-ID: | 199808061537.LAA04956@candle.pha.pa.us |
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Thread: | |
Lists: | pgsql-hackers |
> > > I think the OID auto-casting should be very easy
> > > Once the development tree becomes unbroken...
> > Yes, I think there are some very good reasons to evaluate functions on
> > constants inside the parser.
>
> I wasn't actually suggesting making real changes to the parser. I
> _think_ I can get the OID vs int4 coersion problem fixed with a one-line
> change to a header file, but need a working tree to do it :(
>
> Any progress on getting the tree to compile? Are there some people who
> don't see a problem??
>
> > There are some operations that look at
> > index selectivity that need to know the constant value, rather than
> > knowing if the function returns an int. For example x > 3 looks at
> > the pg_statistics table to see max/min values.
> >
> > You certainly don't want to be evaluating functions on constants
> > inside the optimizer.
>
> ?? Why not? It is an optimization after all. I have never looked at the
> optimizer code however. Are you saying that the current optimizer
> doesn't have a pass or phase where functions could be evaluated? Should
> we add a pass to do this? I've been a bit worried about coding too many
> optimizations into the parser, since they might become pretty obscure
> buried in there.
The optimizer is much too complicated to be putting fmgr() function
calls in there. I know the parser is bad too, but I think it is best to
do it there. We already do some of it there anyway.
--
Bruce Momjian | 830 Blythe Avenue
maillist(at)candle(dot)pha(dot)pa(dot)us | Drexel Hill, Pennsylvania 19026
+ If your life is a hard drive, | (610) 353-9879(w)
+ Christ can be your backup. | (610) 853-3000(h)
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